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Topic: Rat Size (Read 674 times)

Would like to know if male rats are naturally twice as large as female rats. After having eight female rats over nine years, Mr. Ratty and I took in three males, one neutered, two intact. We were both a little startled at how large they are. Their main diet is Oxbow, but they also had children's cereal snacks as treats. Is size governed by glands or diet?

I had one rat, my beautiful sweet Raphael, who was a two-hander, weighing nearly a kilo. His brother and littermate, my beautiful sweet Uriel, was more normal-sized at somewhere in the range of 550 to 640 grams, as I recall. There is sexual dimorphism in Rattus norvegicus, but the size ranges overlap, just as they do in Homo sapiens. In general, bucks are noticeably larger than does, but I wouldn't say that they are normally twice the size, more like 125% to 150%. But if the girls you are used to were on the small side, and your new boys are on the large side, the contrast could very well be more noticeable than usual.

You may be interested to know that among chinchillas (in Chinchilla lanigera, at least), the dimorphism works the other way: the females being quite a bit larger than the males.

Boys are typically larger than girls but it can vary quite a bit.On average, most of my boys have been a little over a pound at adulthood but I've had two who were over a pound and a half and I have one boy who is very light, acrobatic, and feminine in build who only weighs ~500 grams

Most of the girls we have had have weighed around 350-500grams (right at a pound or a bit less)